Re: [PATCH 3/7] bdev: implement freeze and thaw holder operations

[Christoph Hellwig <hch@lst.de>]

On Wed, Sep 27, 2023 at 09:01:42AM -0700, Darrick J. Wong wrote:
> 
> For the bdev->bd_holder_ops == fs_holder_ops case, the freeze_super call
> will call sync_filesystem, which calls sync_blockdev.  If that fails,
> the fsfreeze aborts, and the bdev freeze (at least with the old code)
> would also abort.
> 
> For the !bdev->bd_holder_ops case, why not capture the sync_blockdev
> error code and decrement bd_fsfreeze_count if the sync failed?  Then
> this function either returns 0 with the fs and bdev frozen; or an error
> code and nothing frozen.

Yes, even if that is a behavior change it would be a lot more consistent.
Maybe do the capturing of the error code as a prep patch so that it
is clearly bisectable.

> (Also, does this mean that the new sync_blockdev call at the bottom of
> fs_bdev_freeze isn't necessary?  Filesystems that do IO in ->freeze_fs
> should be flushing the block device.)

Various methods including freeze do the sync_blockdev unconditionally.
I think this is a bad idea and should be moved into the file systems,
but I don't think this is in scope for this series.